Bacteria are everywhere. They have been on Earth for 4 billion years, and have permeated every environmental niche on the planet, including our own bodies! We are, after all, composed of 10 trillion human cells and 100 trillion bacterial cells. But how do you study the Earth's microbiome, and what influence do these bacteria have on our daily lives? On this episode, microbial ecologist Jack Gilbert joins us to discuss a very exciting collaborative study, the "Earth Microbiome Project."